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Toxicodendron rydbergii

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Toxicodendron rydbergii

Secure  (NatureServe)[1]
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Sapindales
Family: Anacardiaceae
Genus: Toxicodendron
T. rydbergii
Binomial name
Toxicodendron rydbergii
  • Rhus rydbergii Small ex Rydb.
  • Rhus radicans var. rydbergii (Small ex Rydb.) Rehder
  • Rhus toxicodendron var. rydbergii (Small ex Rydb.) Garrett
  • Toxicodendron radicans subsp. rydbergii (Small ex Rydb.) Á. Löve & D. Löve
  • Toxicodendron radicans var. rydbergii (Small ex Rydb.) Erskine

Toxicodendron rydbergii, the western poison ivy[3] or northern poison oak, is a species of Toxicodendron in the cashew family native to North America.

Poison ivy berries on a dormant plant in the Wasatch Mountains. Utah, United States.


Unlike Toxicodendron radicans (eastern poison ivy), which often appears as a trailing or climbing vine, Toxicodendron rydbergii is a shrub that can grow to 1 m (3 ft) tall, rarely up to 3 m (10 ft). The leaves are trifoliate and alternate. The leaflets are variable in size and shape, and are usually 15 cm (6 in) long, turning yellow or orange in autumn. On the compound trifoliate leaves, the two leaflets opposite each other are typically asymmetrical, in contrast to the terminal leaflet which always shows bilateral symmetry. The fruits are small, round, and yellowish.[4][5] Like other members of its genus, all parts of this plant contain urushiol, which can cause severe contact dermatitis in most individuals.

Distribution and habitat[edit]

It is native to most of Canada from the Maritimes to British Columbia, and most of the contiguous United States except the Southeast, Nevada, Oregon and California.[6] It is apparently extirpated from West Virginia.[1] It can be found growing in forests, and other wooded areas, usually near streams and rivers.[4]


  1. ^ a b "Toxicodendron rydbergii. NatureServe Explorer 2.0". explorer.natureserve.org. Retrieved 22 September 2023.
  2. ^ "Toxicodendron rydbergii". Tropicos. Missouri Botanical Garden.
  3. ^ USDA, NRCS (n.d.). "Toxicodendron rydbergii". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 11 December 2015.
  4. ^ a b Innes, Robin J. (2012). "Toxicodendron radicans, T. rydbergii". Fire Effects Information System (FEIS). US Department of Agriculture (USDA), Forest Service (USFS), Rocky Mountain Research Station, Fire Sciences Laboratory.
  5. ^ Rydberg, Per Axel 1900. Memoirs of The New York Botanical Garden 1: 268–269 Archived 2018-08-07 at the Wayback Machine as Rhus rydbergii
  6. ^ "Toxicodendron rydbergii". County-level distribution map from the North American Plant Atlas (NAPA). Biota of North America Program (BONAP). 2014.